<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
</head>
<body>
  <script>
    let year = +prompt('请输入年份')
    if(year % 4 ===0 && year % 100 !== 0 || year % 400=== 0){
      alert('闰年')
    }else{
      alert('平年')
    }
  </script>
</body>
</html>